Patent ES-A-2015398 discloses fluid substance recycling and filtering equipment applicable to a meat mass injection machine. The filtering and recycling equipment comprises a pre-filtering unit with a pre-filtration drum arranged to rotate about a horizontal rotation axis and provided with a filtering wall around said horizontal rotation axis, and a safety filtering unit with a safety filtering drum arranged to rotate coaxially together with the pre-filtration drum and provided with a corresponding filtering wall around the horizontal rotation axis.
The brine from the injection machine is poured over an upper region of the pre-filtration drum such that it penetrates into same by gravity through its filtering wall, and exits the pre-filtration drum through an open side wall thereof. The pre-filtered brine is collected in a tub. The safety filtering drum is arranged such that its filtering wall rotates partially submerged in the pre-filtered brine contained in the tub.
The brine of the tub enters into the safety filtering drum through open side walls thereof. The tub has an outlet located below and very close to a lower region of the filtering wall of the safety filtering drum, and the brine is forced out of the safety filtering drum through its filtering wall and through the outlet by suction means. In the upper region of the safety filtering drum there is an automatic cleaning device which uses outside to inside pressurized water jets through the filtering wall.
Patent EP-A-1275305 describes a filtering apparatus applicable to a meat materials injection machine, comprising a pre-filtering unit with a pre-filtration drum arranged to rotate about a horizontal rotation axis and provided with a filtering wall around said horizontal rotation axis, and a safety filtering unit with a pair of safety filtering sleeves horizontally submerged in a tank. The brine from the injection machine is poured over an upper region of the pre-filtration drum such that it penetrates into same by gravity through its filtering wall, and exits the pre-filtration drum through open side walls thereof and through a lower region of the filtering wall. The pre-filtered brine is collected and poured into the mentioned tank inside which the safety filtering sleeves are located. The safety filtering sleeves are connected to an outlet and the brine is forced into the safety filtering sleeves through their filtering wall and through the outlet by suction means.
The safety filtering sleeves can independently pivot towards a straight position emerging from the brine for cleaning and maintenance tasks. A valve device allows operating alternately by means of one of the safety filtering sleeves while the other one is subjected to the cleaning and maintenance operations.
It has been observed that a single pre-filtration drum in the pre-filtering unit may not be enough to provide efficient pre-filtering of the brine from the injection machine, which can still incorporate particles or small pieces of meat mixed therewith, and this results in a higher amount of particles retained by the filtering wall of the safety filter, with the risk of obstruction and the need to perform the cleaning and maintenance operations more frequently.
Document DE-A-2505565 discloses a method for separating suspended material from water using a revolving drum having a microsieve filtering wall. The aqueous suspension is applied onto the outer face of the drum filtering wall, the separated material is then loosened from the drum filtering wall by a water jet from a nozzle directed onto the inner face of the drum filtering wall, and the separated material then flows onto a scraper blade bearing against the outer face of the drum. In a variant, the process is carried out in two stages: first the suspension is applied onto the inner face of a coarse drum with the washing jets on the outside, and then the liquid from this first stage is applied onto the outer face of a microsieve drum with the washing jets on the inside, as in the first variant.
A drawback with the cited DE-A-2505565 is that the use of water jets for washing the drum filtering wall makes unfeasible using the device for filtering brine because the water from the water jets will mix with the brine and will dilute the brine.